The sixth Hanna-Barbera syndicated cartoon after their departure from MGM starred Peter Potamus (a purple hippopotamus), and his traveling companion So-So (a monkey), who fly back and forth through time in a balloon participating in historic events. Whenever they get into serious enough trouble, as they do in every episode, Peter defeats his enemies with his trademark "Hippo Hurricane Hollar." Other cartoon shorts include, "Breezly and Sneely," and "Yippee, Yappee, and Yahooey."
Peter is forced by villagers to get their tax money back from a tyrant. It looks like he will fail until he resorts to using his hippo hurricane holler, which blows the money back to the villagers. The tyrant then announces higher taxes because of the depletion of his treasury and now the villagers are mad at Peter, who escapes in the balloon.
Using the time-space machine, Peter and So-So escape from attacking island natives, a caveman, a WWI flying ace, and a British man-of-war ship before finally landing in the old West. Peter looks just like a bandit on a wanted poster. He's arrested by the sheriff but escapes using his hippo hurricane holler.
Peter and So-So meet Christopher Columbus, who appoints Peter as his emissary to some hostile Indians. Peter fails with negotiations until he resorts to his hippo hurricane holler. The Indian chief capitulates and signs the peace treaty. Columbus gives Peter the title Don Peter Potamus.
Peter and So-So land in America during the time of the Revolution. Peter and So-So spread the word that the redcoats are coming from their balloon. They are shot down by British soldiers. They escape pursuit donning British uniforms but then are chased back to their balloon by American troops.
Peter and So-So end up in Colonial America, where they meet Miles Standoffish. He wants to marry Priscilla, but she refuses to become his wife unless he can prove he's a good provider. Peter helps him by using the Hippo Hurricane Holler to round up wild game. Priscilla agrees to marry Miles, but in the end, it turns out all she wanted was for him to do all the housework while she nagged him to death.
Peter and So-So evade a missile using the time-space machine and end up meeting William Tell. Because William fails to remove his hat in front of the king, he is given the punishment to shoot an apple off his son's head. Since it was Peter's fault, William makes Peter take his place and shoot an apple off So-So's head. Peter misses and is pursued by both the king and William. His hippo hurricane holler causes an avalanche, which enables them to escape.